While each generation of semiconductor technology employs continuous scaling of semiconductor devices, performance parameters of the semiconductor devices are expected to improve, or at least stay at the same level as in previous generation technologies. One such performance parameter is capacitance and resistance of an embedded capacitor. Embedded capacitors are employed to enable an embedded memory device, e.g., an embedded dynamic random access memory (eDRAM) cell, a passive component of a radio frequency (RF) circuit, and decoupling capacitors that provide a stable voltage supply in a semiconductor circuit.
A conventional deep trench capacitor, which is formed in a deep trench within a semiconductor substrate and employs doped polysilicon as a fill material for an inner electrode, provides advantage over a stack capacitor and a planar capacitor in terms of capacitance density and logic process compatibility as an embedded capacitor. The resistivity of doped polysilicon is greater than 1.0×10−4 Ω-cm for even the most heavily doped polysilicon. Further, the resistance of the inner electrode of the conventional deep trench capacitor increases as lateral dimensions of the deep trench capacitor scales with the rest of the semiconductor devices. The increase in the resistance of the polycrystalline inner electrode of the conventional deep trench capacitor adversely impacts high frequency characteristics of the embedded capacitor through an increase in the RC time constant. Thus, performance of an embedded deep trench capacitor having a doped polysilicon inner electrode is degraded for high frequency applications.
While use of a metal inside a deep trench capacitor has been known in the art, the prior art methods present challenges in process integration since introduction of a metal prior to formation of a gate structure may cause metal contamination of semiconductor devices that results in severe degradation of semiconductor performance and reliability. Further, a high-k node dielectric, which is formed within the deep trench prior to formation of the gate structure, is subjected to high temperature cycling that compromises the integrity and reliability of the high-k node dielectric.
In view of the above, there exists a need for a semiconductor structure comprising a deep trench capacitor having a compact size and low resistance that is embedded in a high performance semiconductor structure, and methods of manufacturing the same.
Specifically, there exists a need for a semiconductor structure comprising a deep trench capacitor having an inner electrode of compact size and low resistance and embedded in a high performance semiconductor structure having a high dielectric constant (high-k) gate dielectric and a metal gate, and methods of manufacturing the same.